Such a device is essentially constituted by a concave reflector and a source of light which is generally constituted by the filament of an incandescent bulb which is situated substantially at the focus of the reflector. The center of the reflector has an opening provided with a support for the flange on the bulb. The reflector reflects the light rays it receives from the source into a first approximately parallel and relatively concentrated light beam which is emitted in a substantially horizontal direction; another portion of the light rays leave directly in the form of a spreading conical beam whose axis corresponds to the optical axis of the reflector.
In some applications, a reflector is provided having a window in the top thereof so as to allow a diverging beam coming directly from the filament to pass therethrough in a vertical direction. However, it is observed that the solid angle of this vertical beam is too small since it is partially obstructed by the edge of the bulb support.
Various solutions has been proposed to remedy this drawback.
In American patent U.S. Pat. No. 2,694,138, a second light source is used, thereby increasing the size of the device and its energy consumption.
A mirror is fixed outside the reflector to modify the orientation of the substantially vertical rays leaving the filament directly; this disposition is difficult to mount and the mirror cannot be put into place with sufficient accuracy.
Finally, prisms have been used to deflect the light beam, but as a result a large amount of light is lost by absorption.
It is also observed in the above two solutions that the distribution of light in the deflected beam is not uniform.
The present invention seeks to provide a solution which is simpler and more reliable than prior arrangements.